1. Field of the Invention
The present invention relates to the location services in a telecommunications network. In particular, but not exclusively, the invention relates to intelligent networks (IN)'s in which the IN service is able to control call setup based on the location of a mobile station (MS). The invention may also provide methods to supply IN service with location of a mobile station with minimum delay for call establishment (or setup) procedure.
2. Description of Related Art
An intelligent network (IN) is a telecommunications network architecture which can relocate services and databases via switches to one or more control/decision nodes to thereby provide intelligent control of a call or other event. The GSM network for example, offers IN-based services. These services can be “forwarded” at any stage when a subscriber having access to a mobile network is abroad in a foreign country with which the home operator has a reciprocal roaming agreement.
Customized applications for mobile network enhanced logic “CAMEL” is the GSM and UMTS arrangement which makes operator-specific services available to subscribers who are outside their own network.
A basic idea behind the architecture of INs is to make the service logic independent of switching and transport in the network. The network functions which provide these attributes and which form the IN architecture are service switching and service control. Service switching is found in a service switching point (SSP), which is a node with functions to detect calls to the IN service, and the service control point (SCP) which is a generally centrally located node and which contains the logic and data for the IN services.
The location services (LCS) feature in GSM and UMTS provides the mechanism to support mobile location services of operators which are not covered by standardised GSM or UMTS services. LCS utilizes one or more positioning mechanisms in order to determine the location of an MS. Positioning of a target MS involves two principle steps. These are signal measurements and location estimation in which the location is calculated based upon the measured signals.
A number of location estimating mechanisms are known for use with LCS. These are the time of arrival (TOA), enhanced observed time difference (E-OTD), observed time difference of arrival (OTDOA), and global positioning system (GPS) positioning mechanism. Through use of one of these the LCS provides means to locate a mobile station. The public land mobile network (PLMN) will thus provide a location application with the geographical location of the MS. The location application which uses this information may reside within the PLMN (in either the MS or in the network itself) or outside the PLMN (in an external application).
Positioning may be initiated either by the network or an external application. The role of the core network nodes in relation to the LCS is to convey positioning requests towards the serving mobile location centre (SMLC) and location information towards the requesting gateway mobile location centre (GMLC). Furthermore, the core network nodes may identify events such as emergency call setups which will require initiation of positioning of a mobile station.
In the past the procedure by which position information of the MS has been provided to the IN has been reactive. That is to say when a call to/from a MS has been requested, the location of the MS has then been calculated, if it was needed for a value added service (e.g. an IN/CAMEL service) This has the problem of delaying the call establishment until after the location has been established.
It is an object of the present invention to at least partly mitigate the above-referenced problems.